Fix miscalculated buffer sizes

For the Pico DaynaPORT target, the debug buffer and the prefetch buffer
were not a power of 2 or multiple of 512 respectively. Fixing the values
in platformio.ini resolved a logging zululog.txt issue.

platformio.ini

@@ -165,8 +165,8 @@ build_flags =
     -DZULUSCSI_NETWORK
     -DZULUSCSI_DAYNAPORT
 ; These take a large portion of the SRAM and can be adjusted
-    -DLOGBUFSIZE=8138
-    -DPREFETCH_BUFFER_SIZE=8138
+    -DLOGBUFSIZE=8192
+    -DPREFETCH_BUFFER_SIZE=8192
     -DSCSI2SD_BUFFER_SIZE=57344
     ; This controls the depth of 2 x NETWORK_PACKET_MAX_SIZE (1520 bytes)
     ; For example a queue size of 10 would be 10 x 2 x 1520 = 30400 bytes